A. Technical Field
The present invention relates to: a micro-powdery stain composition for an unsaturated polyester resin; an unsaturated polyester resin composition; and a production process for the unsaturated polyester resin composition.
B. Background Art
Generally, molding processes of FRP are, for example, as follows: a process comprising the step of press-molding a molding material such as SMC (Sheet Molding Compound) or BMC (Bulk Molding Compound) as obtained by molding an unsaturated polyester resin composition into a sheet or bulky shape respectively, wherein the unsaturated polyester resin composition is prepared by combining an unsaturated polyester resin with a low-shrinkage agent, a filler, a stain, a glass fiber and so on; and a hand-lay-up-molding process comprising the step of coating a stain resin, which is called gel coat, to a mold by spray- or hair-coating, and then reinforcing the coated matter with a glass fiber or unsaturated polyester resin. The stain, used in these molding processes, is a pasty stain which is obtained by kneading an unsaturated polyester resin, a plasticizer, and either or both of a pigment and an oil-soluble dye using a three-roll mill, a bead mill, or the like.
The unsaturated polyester resin is usually a solution in which a liquid polymerizable monomer such as a styrene monomer is used as the solvent, so there is a merit in that the pasty stain is easy to disperse because liquids easily disperse into each other, but there are various problems in that the gelation or the increase of the viscosity occurs when conserving the stain, and the usage therefore becomes impossible, and in that color differences or color separations occur due to sinking of substances of heavy specific gravity such as titanium oxide.